MATERIAL REQUIRED
Conical flask, thistle funnel and delivery tube fitted with cork, pneumatic trough, beehive shelf, gas jar, hydrogen peroxide, manganese dioxide
THEORY
Oxygen is an abundantly occurring element on the earth. It constitutes about 49% in the form of various oxides of the earth’s crust. It is occurred in a free state as well as in a combined state. Oxygen is found in the free state in air. In the combined state, it is richly found in combination with other elements in water, sand, acids, alkalis, carbohydrate, fat, wood, etc. In the human body, it occupies about 72%.
There are a lot of laboratory processes for producing oxygen. Among them, one of the most common ways of preparation of oxygen is in a laboratory is hydrogen peroxide method where hydrogen peroxide decomposes to water and oxygen this reaction occur automatically in presence of sunlight but it is very slow process. This reaction become very fast with the help of catalyst Manganese Dioxide. The reaction is exothermic. Hence it produce heat.
Hydrogen Peroxide → Water + Oxygen
2H₂0₂(aq) → 2H₂O(L) + O₂(g)
PROCEDURE
- Take a clean dry conical flask with small amount of manganese dioxide.
- Fit cork with thistle funnel and delivery tube.
- Cover another end of delivery tube by beehive shelf in water trough.
- Filled water trough with two third of water.
- Take a gas jar and filled with water and cover by glass plate without producing bubble at top.
- Pour about 30 ml of hydrogen peroxide through thistle funnel. Thistle funnel must be dipped in hydrogen peroxide.
- Wait about 30 seconds to escape air bubble from delivery tube for complete removal of air from conical flask.
- Then invert gas jar with glass plate over the beehive shelf under water in water trough.
- Finally remove glass plate.
- Then oxygen gas is collected in gas jar by downward displacement of water.
OBSERVATION
- Oxygen gas is collected by downward displacement of water.
- When burning 🔥 wood piece is inserted it glow brightly.
- Conical flask is heated during reaction
RESULT
- Oxygen gas support burning.
- It is lighter than air.
CONCLUSION
Oxygen gas can be prepared in laboratory by decomposing hydrogen peroxide with catalyst manganese dioxide.
PRECAUTION
- The apparatus should be airtight.
- The stem end of the thistle funnel should be dipped in the hydrogen peroxide.
- The inflammable and burning apparatus should be kept away while preparing oxygen gas as oxygen is a supporter of combustion.
- We should not collect the first few bubbles as it is the air of the delivery tube. So, it should be driven out before collecting in a gas jar.
- Pure manganese dioxide should be used as a catalyst.
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